Results:
Scientists from Johns Hopkins University found that a complex
combination of treatments, including stem cells and growth factors, can
heal damaged neural circuits, allowing partially paralyzed rats to
walk. According to the findings, 11 out of 15 rats with spinal-cord
injuries regained some motor function after receiving the full battery
of treatments.

Why it matters: Previous studies
on paralyzed rats demonstrated the possibility of boosting the function
of the nervous system and improving motor skills. But this is the first
study to show that newly grown nerve fibers can emerge from the spinal
cord, extend all the way to ­muscles in the rats’ haunches and limbs,
and form functional connections with them. These findings represent a
significant step forward in regenerative medicine, providing new
treatment possibilities for some types of spinal-cord injury and for
diseases in which motor neurons are damaged, such as amyotrophic
lateral sclerosis (ALS).

Methods: The
researchers transplanted motor neurons, derived from embryonic stem
cells, into the spinal cord. Then they added a mix of growth factors to
help the new cells survive and grow, as well as two chemicals known to
block the signals that normally keep nerve fibers from growing out of
the spinal cord.

In order to get the newly sprouted fibers to
span the wide gap between the spinal cord and the muscles, the
researchers injected neural stem cells into the target muscles. These
cells produced a nerve growth stimulator that drew growing motor
neurons to the muscle and allowed them to make functional neuromuscular
connections.

Next steps: The team is now
planning tests in pigs. Studies in larger animals are necessary to make
sure that the new neurons can grow to great enough lengths that the
treatment will work in humans. If those experiments are successful, the
scientists say, human clinical trials could begin within five years.